Immunostimulatory compositions and methods of use thereof

Abstract

Lipid conjugates for enhanced delivery of cargo to the lymph nodes are disclosed. The lipid conjugates typically include three domains: a lipophilic domain that binds to albumin, a polar block domain, and a cargo such as a molecular adjuvant or immunostimulatory compound (such as an oligonucleotide) or antigenic peptide. Depending on the cargo, the length and compositions of the polar block can be tailored to push the equilibrium toward albumin binding, stable micelle formation, or cell insertion. The conjugates can be administered to a subject, for example, a subject with cancer or an infection, to induce or enhance a robust immune response in the subject.

We claim: 
     
       1. An amphiphilic albumin-binding conjugate comprising
 (a) a lipid component; 
 (b) an optional polar component; and 
 (c) an immunomodulatory compound or molecular adjuvant; 
 wherein the immunomodulatory compound or molecular adjuvant is bound directly to the lipid or is bound to the lipid via a linker, 
 wherein the conjugate is sufficiently soluble that the lipid binds to albumin under physiological conditions, and 
 wherein a plurality of the conjugates can spontaneously form micelles in aqueous solution. 
 
     
     
       2. The conjugate of  claim 1  wherein the immunomodulatory compound or molecular adjuvant is bound to the lipid via a linker. 
     
     
       3. The conjugate of  claim 2  wherein the linker is an oligonucleotide linker. 
     
     
       4. The conjugate of  claim 3  wherein the oligonucleotide linkers comprises “N” consecutive guanines, wherein N is between 0-2. 
     
     
       5. The conjugate of  claim 4  comprising the structure L-5′-Gn-ON-3′, wherein “L” the lipid, “G” is a guanine, “n” is 0-2, and “ON” is the immunostimulatory oligonucleotide. 
     
     
       6. The conjugate of  claim 1  wherein the conjugate exhibits increased accumulation in the lymph node when administered to a subject in vivo compared to administration of the immunostimulatory oligonucleotide alone. 
     
     
       7. The conjugate of  claim 1  wherein the lipid is a diacyl lipid. 
     
     
       8. The conjugate of  claim 7  wherein the acyl chains of the lipid comprise 12-30 hydrocarbon units. 
     
     
       9. The conjugate of  claim 1 , wherein the immunomodulatory compound or molecular adjuvant is an oligonucleotide. 
     
     
       10. The conjugate of  claim 9 , wherein the oligonucleotide is an immunostimulatory oligonucleotide. 
     
     
       11. The conjugate of  claim 10 , wherein the immunostimulatory oligonucleotide is sufficiently polar to reduce the ability of the lipid to insert into a cellular plasma membrane. 
     
     
       12. The conjugate of  claim 10  wherein the immunostimulatory oligonucleotide binds a pattern recognition receptor. 
     
     
       13. The conjugate of  claim 12  wherein the immunostimulatory oligonucleotide comprises CpG. 
     
     
       14. The conjugate of  claim 13  wherein the immunostimulatory oligonucleotide is a ligand for a Toll-like receptor. 
     
     
       15. The conjugate of  claim 10  wherein the immunostimulatory oligonucleotide has a phosphorothioate (PS) backbone. 
     
     
       16. The conjugate of  claim 10  wherein the immunostimulatory oligonucleotide comprises 20 or more nucleic acids. 
     
     
       17. A vaccine adjuvant comprising a plurality of the conjugate of  claim 1 . 
     
     
       18. The conjugate of  claim 2  wherein the linker is selected from the group consisting of hydrophilic polymers, a string of hydrophilic amino acids, polysaccharides or a combination thereof. 
     
     
       19. The conjugate of  claim 2  wherein the linker comprises “N” consecutive polyethylene glycol units, wherein N is between 25-50. 
     
     
       20. An immunogenic composition comprising the adjuvant of  claim 17  and an antigen. 
     
     
       21. The immunogenic composition of  claim 20  wherein the antigen is an amphiphilic peptide conjugate comprising a peptide antigen which (i) is conjugated directly to a lipid, or (ii) is linked to a linker which is conjugated to a lipid, wherein the lipid binds to albumin under physiological conditions, and wherein the peptide antigen, the linker, or the peptide antigen and linker in combination are sufficiently polar to reduced or inhibit insertion of the lipid into a cell's plasma membrane. 
     
     
       22. A method of increasing an immune response in a subject comprising administering the subject an effective amount of immunogenic composition of  claim 20  to increase the immune response in the subject. 
     
     
       23. The method of  claim 22  wherein the immune response is an increase in the number of CD8+ T cell expressing TNF-α or IFN γ TNF or INF compared to a control. 
     
     
       24. The method of  claim 22  wherein the subject has cancer or an infectious disease. 
     
     
       25. A method of treating cancer or an infectious disease comprising administering to the subject an effective amount of the immunogenic composition of  claim 20  to reduce one or more symptoms of the cancer or infectious disease compared to a control.